Research Of Si-C Hybrid Electrodes For Lithium-ion Battery

Lithium-ion battery is the essential part of the energy storage system, which is in the widely attention. Carbon anode materials is commonly used in lithium-ion battery at present, but it is difficult to adapt to the requirements of high performance energy storage materials, due to its lower specific capacity. It is necessary to research new anode materials. Silicon will be a good choice, which has high specific capacity, low voltage platform and abundant reserves. It is very difficult to put silicon into commercial production and application, because silicon particles has volume effect in the process of charging and discharging, which is easy to cause destruction of electrode conductive network. In order to overcome these defects, we research silicon –based anode materials. Best proportion of S/C was studied. On this basis. We used carbon nanotubes and graphene as the doping modificationThe research contents could be seen as follow:(1)Silicon/graphite composite material preparation. Micro silicon and graphite homogeneous mixed have been prepared by simple mechanical ball grinding method. the influence of different doped silicon ratio on electrochemical performance of composite materials have been studied. The results show that when the silicon doping amount is achieved 20%, the silicon/graphite composite has the best electrochemical performance with the charge capacity of 567 mAh g-1 and capacity retention rate was 58.6% after 10 times circulation,which is due to the synergy of silicon and graphite.(2)Silicon/graphite/grapheme composite material preparation. First, micro silicon and graphene homogeneous mixed have been prepared by simple mechanical ball grinding method. Then preparing composite compound with graphite,finally get silicon/graphite/graphene composite. We study the influence of different doped graphene ratio on electrochemical performance of composite materials. Research show that the composite exhibited a high charge capacity of 499.9mAh g-1 and 520.9mAh g-1, and capacity retention rate was 98.2% and 92.3 after 10 times circulation, when the graphene doping amount achieve 3% and 5%. The two-dimensional layered structure can effectively restrain the expansion of the silicon particle breakage and form good conductive network, eventually improve the electrochemical performance.(3)Silicon/graphite/carbon nanotube composite material preparation. First, micro silicon and carbon nanotube homogeneous mixed have been prepared by simple mechanical ball grinding method.Then make composite compound with graphite and finally get silicon/graphite/carbon nanotube. We study the influence of different doped carbon nanotube ratio on electrochemical performance of composite materials. Research show that the composite exhibited a high charge capacity of 455.4mAh g-1 and 462.4mAh g-1, and capacity retention rate was 81.4% and 82.1% after 10 times circulation, when the carbon nanotube doping amount achieve 7% and 9%. MWCNTs whisker structure can effectively increase the conductivity of the composite and form good conductive network, then improve the electrochemical performance.